I haven't had really hot heat yet this winter and last weekend I finally decided to do something about it.

At first, my car would get into operating range while driving around the city, but on the highway would almost dip below the coldest mark....right, so thermostat must be stuck open.

Replaced the thermostat and sure enough at highway speed, it stays at operating temperature now. I also had heat on the way home from the thermostat change....actually had to turn it off of max heat.

However, I parked the car, came back to it two days later, got into operating temperature, but no climate heat.

When I filled the coolant after changing the thermostat, I had the cap off until it started circulating and kept filling as needed as lil air bubbles came popping out; I'm 85% certain I have all the air out of the system. The reservoir is also at a good level between full and fill after I capped everything from the filling.

Some further information:
1) when I adjust the temperature control from hot to cold, it gets really damn cold (ac off)
2) the hoses going in and out of the heater core are both fairly hot
3) when I turn the fan off, count to 10, and turn to full blast the air feels warmer than it usually is, but it could be a subjective feeling...hands are getting cold in that 10 seconds, then adjust to the heat shortly after
4) the resevoir is sitting where the upper intercooling piping USED to go (beside the air intake) (I have a short route so I had to move the resevoir out of the way), the top of the tank is a little lower than the rad cap, but I read somewhere that it is supposed to be equal with or lower than the thermostat...is that true?
5) there are no coolant leaks, park the car, idle it, whatever, not a single drop of coolant

It seems there are four reasons for poor heat:
1) Thermostat stuck open
2) low coolant or air in system
3) clogged heater core
4) blend door not doing its job

So,
1) thermostat is fixed now
2) just filled, no leaks, kept circulating with cap off until there were no more air bubbles
3) both hoses are hot
4) when switching from hot to cold, it gets damn cold, and after I just changed the thermostat, I had really hot air blowing on the drive home (30mins) from the shop I did the work in

Based off of this information, what would be my next in line to test/fix? What additional checks can I do?

Thank you in advance.

Your on the right path to diagnosing and repairing the problem. I would say the poor heat lies between reasons 3 and 4.

So had another chance to play around with it and think I know for sure that it is the heater core and probably back flushing it will probably help it out.

When the heater is 'cold' the hoses run the same temperature, but when the heater is 'hot' there is a noticeable difference in the temperatures of the hoses...something I didn't check before, I had the heater on cold when I changed the thermostat and felt the hose differences.

I also was able to poke my head under the console and the pin the temperature switch operates on does appear to be moving its full range.

So I am going to try to flush the heater core tomorrow and see how that works out.

What is the best way to fill to make sure you have no air in the system?

How are you flushing the heater core? I am very interested in this as my Jeep does not heat up properly.

With a garden hose and an attachment for the hose. Backwash, obviously from the back first. Debree sometimes comes out but generally just NOT clean water. Do the reverse. Backwash again. And the reverse again.

That generally works for me.

Just back flushed...and didn't have anything come out other than clean, clear water...and those hoses were the worst thing I have ever done on my car yet, and I changed the slave clutch cylinder in -20C weather on the street.

So yes, got a high pressure hose pumped it through the top hose, ran until clear (didn't take long at all), attached to bottom, ran until clear...attached to top...attached to bottom, done.

To get at the hoses I removed the battery and unbolted the cruise control and lifted out of the way. To get the hoses actually off, I wish I had a 90degree flat head to pull the hose towards me, but I just had a 45. After switching between the 45 and the heat gun, they eventually came off. When I put them back on, I used a bit of Loctite 515 around the copper tubes and slid the hoses back on.

So no, heater core wasn't plugged. This time I got really stubborn and ran my car until I didn't see a single lil bubble pop up from the rad cap. Before, I saw the lil bubbles and thought screw it, they won't hurt anything...well they must have hurt something because after I put the cap on this time, the heat was BURNING! I sweated on the way home because I refused to turn the heat off

In the end, it was air...somehow. I'll have to see how it does after tomorrow because something might be amiss with my reservoir.

Thanks.

What I noticed with DSM's is that I can run it forever, and somehow the air doesn't always come out. So what I've noticed is I let it get to operating temperature and let the coolant start to move and top it up as needed (with the overflow pinched off), do that until the coolant stay at the top, (usually takes about 5 mins). Cap it off, go for a spirited drive, some pulls, come back, shut the car off and let it cool for about an hour or so. Come back out and do it again. I find that this is the only way to properly get the heat working on these cars.

Hi all

I am having a simular problem, no heat.
I have a 1995 Eagle Talon TSi.

So far the thermostat has been changed, the coolant changed and the system flushed, the heater core flushed until the water coming out is clean. Still no heat. The fan works, air comes out, but it barely warmer than the outdoor air.

My mechanic put a valve on the output hose from the heater core to check for air in the system. No air, sometimes the pressure is good (coolant sprays out if the value is opened), sometimes the pressure is low (no spray). It can change from minute to minute. Also, the coolant level at the rad cap can be up or down from minute to minute.

The mechanic has no idea what is going on and has given up.
If anyone knows what the problem is and how to get heat I would really appreciate it.

Thanks,
Brian Monk

From what I just went through, I would say air is getting into the system. Check the lines from the coolant reservoir (make sure it has coolant in it too). Rad cap might also be a cause of air in the system.

Are there any coolant leaks?

When you switch the temperature from hot to cold, does it get cold? Are the linkages for the blend door working?

Pop off the rad cap, run it to operating temperature and don't stop running until you don't see a single bubble coming out of the filler neck. At the same time, keep the coolant level just slightly above the passages so you can see the bubbles and air isn't getting dragged into the rad.